Yeah, but ONE good choice doesn't make up for a lifetime of evil, IMHO. And it still doesn't mean that when he turned he was being a cowardly traitor. I am of the opinion that fear played a big part in Anakin's downfall, probably not as a coward though, implying he was afraid for himself. His fear for his loved ones will be his undoing, I'm afraid. Luckily Luke proved to be much stronger at staying the course of light.